Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH DRILLING; MINING
  • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B47/00—Survey of boreholes or wells
  • E21B47/09—Locating or determining the position of objects in boreholes or wells, e.g. the position of an extending arm; Identifying the free or blocked portions of pipes
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH DRILLING; MINING
  • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B47/00—Survey of boreholes or wells
  • E21B47/01—Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V5/00—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity
  • G01V5/04—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
  • G01V5/08—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
  • G01V5/10—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
  • G01V5/104—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources and detecting secondary Y-rays as well as reflected or back-scattered neutrons
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V5/00—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity
  • G01V5/04—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
  • G01V5/08—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
  • G01V5/12—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using gamma or X-ray sources
  • G01V5/125—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using gamma or X-ray sources and detecting the secondary gamma- or X-rays in different places along the bore hole

Definitions

• the invention relates generally to the field of logging a borehole. More specifically, the invention relates to determining the appropriate time and/or location to activate a tool conveyed downhole.
• Downhole tools can be conveyed in multiple ways as they are lowered into the borehole or while drilling the borehole.
• Traditional approaches are the conveyance of the tool on wireline by lowering the tool on a cable that also provides power to the tool and communication between the tool and the surface.
• the tool can be conveyed by slickline.
• the tool is lowered on a cable that is used solely to convey the tool but does not provide power or communication.
• the tool functions in an autonomous way and has its own downhole power (typically batteries). Limited down communication can be achieved by accelerating the cable in a certain pattern.
• Tools can also be conveyed at the bottom of drill pipe (e.g., Tough Logging Conditions or "TLC”) if borehole conditions do not allow the tool to reach the bottom of the hole. This may be of particular interest in highly deviated or horizontal wells, where gravity will not allow the tool to reach the bottom of the well. In this kind of logging the wireline is inside the drill pipe and the logging therefore is very similar to traditional wireline logging.
• TLC Tough Logging Conditions
• Pushing tools down on a drill string may result in damage to the tools as they are used to push past obstacles in the wellbore.
• the operation of TLC is expensive and often requires logging cable and a logging truck.
• An alternative method is to deploy the tool through drill pipe, letting it exit the drill pipe and latch it to the bottom of the drill pipe. Once this is done, the drill pipe is pulled out of the hole while the tool is logging and recording the data in its internal memory.
• the enabling of the tool power and opening of a caliper is generally based on a timer. This timer is set just before the tool is lowered into the drill pipe to be pumped down. The setting generally has to leave enough time to allow for the tool to be pumped down and deployed. As there can be multiple delays in the deployment this time has to be set very long (i.e., building in excess time). If the deployment is quick then there is a long wait after the deployment before the tool can start moving up.
• Figure 1 is a diagram of a tool within a drill pipe, according to an example embodiment
• Figure 2 is a diagram of a density tool deployed within a borehole 214, according to an example embodiment.
• Figure 3 is a graph plotting depth versus the count rates of the short-spaced detector and the long- spaced detector, according to an example embodiment.
• Figure 4 is a graph plotting depth versus long-spaced apparent density, short- spaced apparent density, and the compensated density (RHOB) when the tool is in casing or drill pipe, according to an example embodiment.
• Figure 5 is a graph plotting the channel versus long-spaced energy spectrum in and out of the casing, according to an example embodiment
• Figure 6 is a graph plotting the channel versus short-spaced energy spectrum in and out of the casing, according to an example embodiment
• Figure 7 is a graph plotting the windows ratios W1/(W3+W4) for the short-spaced and long-spaced detectors, according to an example embodiment.
• Figure 8 is a graph plotting depth versus the long-spaced and short-spaced apparent photoelectric factor (PEF), according to an example embodiment.
• Figure 9 is a diagram of a neutron tool, according to an example embodiment.
• Figure 10 is a graph plotting depth versus the count rates of the near detectors and the far detector, according to an example embodiment.
• Figure 11 is a graph plotting depth versus thermal neutron porosity (TNPH) and thermal alpha factor (TALP), according to an example embodiment.
• Figure 12 is a graph plotting depth versus an exemplary Near/Far thermal count rate ratio and also an exemplary (Near Thermal)/(Near epithermal) count rate ratio, according to an example embodiment.
• Figure 13 is a flow diagram of an auto-detect algorithm or method, according to an example embodiment.
• Figure 1 is a diagram of a tool 102 within a drill pipe, according to an example embodiment.
• the example tool 102 is shown disposed within an inner housing or protective sleeve 104 and within an outer housing or special drill pipe 106.
• either or both of the protective sleeve 104 and the special drill pipe 106 can be made from steel.
• the tool 102 can be surrounded by about 0.55 in of steel (cumulatively between the protective sleeve 104 and special drill pipe 106).
• the materials making up the protective sleeve 104 and special drill pipe 106 can include about 1% manganese and 1% chromium.
• the inner gap 108 between the tool 102 and the protective sleeve 104, as well as the outer gap 110 between the (centralized) protective sleeve 104 and the special drill pipe 106 are filled with drilling mud.
• the flow of drilling mud through these gaps can, in example embodiments, assist in carrying the tool 102 downhole through the drill pipe until the protective sleeve 104 and tool 102 reach the end of the drill string.
• the special drill pipe 106 may be different from ordinary drill pipe in that it is the last joint of drill pipe in the drill string.
• the special drill pipe 106 also can include some type of latching mechanism (not shown) for attaching to the tool 102 when the tool 102 is ejected from the protective sleeve 104.
• the special drill pipe 106 can comprise a material and configuration substantially identical to or similar to the rest of the drill pipe, and may simply be the final joint of the drill string.
• the special drill pipe 106 can have a different configuration to better house the latching mechanism.
• the latching mechanism can arrest the motion of the tool 102 relative to the drill pipe, once the tool 102 is substantially exposed.
• FIG. 2 is a diagram of a density tool 212 (which can be the tool 102 represented in Figure 1) deployed within a borehole 214, according to an example embodiment.
• the tool string carrying the density tool 212 is latched to the end of the drill string, as described above.
• the density tool 212 is disposed within a borehole 214 of a formation 216.
• the density tool 212 includes a density pad 220, a long-spaced detector 222 and shield 224, a short-spaced detector 226 and shield 228, and a gamma-ray source 230.
• the density tool 212 also can have a caliper arm 232 hingedly connected to the tool via a hinge 234, with mechanics for operating the caliper in a caliper mechanical section 236.
• the caliper arm 232 can be in extended position, extended such that the caliper arm 232 makes contact with (or approaches contacting) the borehole 214 wall.
• the caliper hinge 234 additionally allows the caliper to be in a recessed position (not shown) in which the caliper can be generally in line with the axis of the tool.
• the use of the density measurement in conjunction with the opening of the density caliper can be attractive since the measurements are collocated.
• permission to open the caliper can be based on a voting system, in which some measurements can veto the opening.
• the caliper can start opening in certain embodiments. If at the end of the process of opening the caliper, the measured diameter is below a predetermined value, the caliper can be closed again in certain embodiments. A new attempt can be made after a predetermined wait time. In example embodiments, a new attempt at opening the caliper will only be made when the measurement conditions are satisfied.
• the fact that the caliper can be opened and that the tool is deployed can also be used to provide a signal to power up all the tools in the string, if this has not already happened.
• measurements made by a density tool 212 can be used to help determine whether the density tool 212 has been deployed from the drill string (and therefore the caliper arm 232 can be extended), or whether instead the density tool 212 is still within the drill pipe (in which case the caliper arm 232 should not be extended). Certain examples of the significance of these measurements made by a density tool 212 will now be described with reference to the following Figures 3-8.
• the measurement of the density tool 212 inside drill pipe is similar to the situation of the tool inside casing, and thus an estimate of a response of a density tool 212 being within a drill pipe can be obtained by looking at the density tool 212 response in casing.
• An example of the effect of casing is shown in Figure 3, which is a graph plotting depth versus the count rates of the short- spaced detector 226 and the long- spaced detector 222, according to an example embodiment.
• the count rate line 340 corresponding to the short- spaced detector 226 i.e., in certain embodiments, the detector closer to the gamma-ray or x-ray source 230
• the count rate line 342 corresponding to the long-spaced detector 222 drops less significantly. It is understood that the count rates may need to be calibrated using a calibration reference in order to take into account source 230 strength differences and tool-to- tool response differences.
• Figure 4 is a graph plotting depth versus long-spaced apparent density 444, short- spaced apparent density 446, and the compensated density (RHOB) 448 when the tool is in casing or drill pipe, according to an example embodiment.
• RHOB compensated density
• all three density lines jump as the tool enters casing or drill pipe.
• the largest effect is seen on the short-spaced density. This can be due to the larger relative change in count rate and the lower density sensitivity of the short-spaced detector 226, i.e. a small change in the short-spaced count rate corresponds to a large change in the apparent density.
• the long- spaced density which has a deeper depth of investigation, can be less affected, as shown in Figure 4.
• the compensated density (RHOB) drops to a lower value (overcompensation).
• Figure 3 and Figure 4 show that there can be a significant effect of steel surrounding the tool on the total count rates and the density answer. Although they change significantly, the count rates may not always give an unambiguous indication of whether the tool is in casing. Looking at the apparent densities shows that entering into casing or drill pipe can lead to a sharp increase in the difference between the long-spaced and short-spaced apparent densities. This will result in a large negative deltaRho. As will be discussed herein, this fact can be exploited to detect whether the tool is inside drill pipe.
• the presence of iron around the tool also can have a strong effect on the spectral shape. Absorption of low energy gamma-rays in the iron can remove most of the low energy part of the spectrum.
• Figure 5 is a graph plotting the channel versus long-spaced energy spectrum in 550 and out 552 of the casing according to an example embodiment
• Figure 6 which is a graph plotting the channel versus short-spaced energy spectrum in 654 and out 656 of the casing according to an example embodiment.
• FIG. 7 is a graph plotting the windows ratios 758, 760 W1/(W3+W4) for the short-spaced 226 and long-spaced detectors 222, according to an example embodiment.
• Wl represents the low energy window (soft radiation)
• W3 and W4 the high energy part of the spectrum (hard radiation).
• Low energy gamma-rays or x-rays are not very penetrating and are often called soft radiation. Radiation with higher energy is significantly more penetrating as is therefore called hard radiation.
• a dramatic change in the windows ratios for both the short-spaced 226 and long-spaced detectors 222 occurs in example embodiments when the tool goes from outside the casing to inside the casing.
• Figure 8 is a graph plotting depth versus the long-spaced 864 and short-spaced
• the graph thus illustrates an example effect the casing has on PEF.
• PEF apparent photoelectric factor
• other or additional approaches can be used for determining the presence of a tool inside casing or drill pipe.
• the determination of density, PEF, and borehole 214 parameters like borehole 214 fluid density, presence of barite, standoff, and the like can be based on a forward model based on multiple spectral windows.
• An example density tool 212 for making these measurements can be the PLATFORM EXPRESS density tool of the assignee of the present application.
• An inversion of the forward model can give an indication of the presence of the tool in drill pipe.
• the presence of drill pipe can be inferred from the reconstruction error when solving for the quantities above when using a model valid for open hole only.
• An open hole forward model does not properly describe the cased hole environment. When inverting the forward model to obtain the unknowns, this will result in a poor fit or reconstruction. Therefore a large reconstruction error would be indicative of the presence of casing.
• a model including the presence of drill pipe can be used.
• An example inversion can solve for a quantity related to the presence or absence of drill pipe. An example of such a quantity is the thickness of steel surrounding the tool.
• the inversion of an OH forward model may attempt to solve for tool standoff, mud weight and mud Pe (photoelectric effect).
• the inversion may show increased mud weight and mud Pe and therefore signal the presence of casing. If the forward model includes a cased hole description, then it will solve for casing thickness and the presence of casing will be directly indicated by the inversion.
• a database and a neural network can be used to detect the presence or absence of drill pipe.
• a neural network which is properly configured, will attempt to find the best match between a database of known situation (responses) and the observed response. If the database is limited to open hole, the neural network will indicate the lack of an acceptable solution. If a cased hole (including drill pipe) characterization is in the database the neural network will indicate the presence of casing and/or drill pipe.
• Such inputs may be the casing weight (typically given in lb/ft), mud weight, drill pipe inner and outer diameter to name a few.
• Other methods consistent with this disclosure can be used, as may be recognized by one of ordinary skill in the art having benefit of the present disclosure.
• a neutron tool response can be used to try and determine whether the tool is inside the carrier or deployed.
• the neutron tool may provide three count rates on which the determination can be based. Other numbers of count rates are also possible.
• neutron tool information can be used to corroborate the results obtained from density. As with the density measurement, the count rates alone may not give sufficient information to allow a vote.
• a resistivity measurement is collocated with the density measurement on the same pad.
• the resistivity measurement may show very low resistivity in the presence of drill pipe or casing. This low reading may be used to determine whether the tool is inside drill pipe.
• there could be a simple dedicated resistivity measurement e. g. one or more resistivity measurement buttons collocated with the density measurement or close to it, which are used for the detection of casing or drill pipe.
• Such a measurement device could also be installed on the caliper arm.
• an ultrasonic device on the density pad (or mandrel) collocated with the density measurement or within a short distance of it.
• the ultrasonic measurement is sensitive to the presence of drill pipe or casing and the measurement may be used to determine whether the tool is in drill pipe.
• Yet another collocated measurements could be a dielectric measurement (Schlumberger Dielectric Scanner), which is very sensitive to the presence of drillpipe or casing.
• Figure 9 is a diagram of a neutron tool 966, according to an example embodiment.
• the neutron tool 966 contains a neutron source 968 (e.g., an AmBe source 968, but the source 968 need not be limited to the use of a radioisotope source). Additionally, the neutron tool 966 can include three neutron detectors. Two detectors can be mounted side-by-side at a first axial spacing from the source 968. One of these detectors can be a detector of epithermal neutrons (e.g., the near epithermal detector 970), the second detector (e.g., the near thermal detector 972) can be a detector of thermal neutrons— including epithermal ones. A third detector— the far detector 974, which can be a thermal neutron detector, is at a farther axial spacing.
• a neutron source 968 e.g., an AmBe source 968, but the source 968 need not be limited to the use of a radioisotope source.
• the neutron tool 966 can include three neutron detectors. Two detectors can be mounted side-by-side
• the neutron tool 966 can further include a tool housing 976, as well as shielding 978 and backshielding 980.
• count rates may need to be calibrated to a reference calibration standard in order to account for variability in source 968 strength and tool-to-tool response differences.
• measurements of the neutron tool 966 inside drill pipe is similar to the situation of the tool inside casing, and thus an estimate of a response of a neutron tool 966 being within a drill pipe can be obtained by looking at the neutron tool 966 response in casing.
• An example of the effect of casing is shown in Figure 10, which is a graph plotting depth versus the count rates of the near detectors (thermal 972 and epi-thermal 970) and the far detector 974, according to an example embodiment. As the tool enters the casing (e.g., shown by the line at approximately 165 ft of depth), the thermal count rates 1082, 1086 drop sharply.
• the low count rates are still in the range of the count rates that could be observed in open hole at high porosity and/or salinity.
• the count rates may therefore not give an unambiguous indication whether the tool is inside the casing (or inside the deployment sleeve).
• the count rate 1084 of the epithermal detector 970 shows virtually no change when entering the casing. This could be an indication that ratios of count rates could be used to detect the transition from cased to open hole.
• Figure 11 is a graph plotting depth versus thermal neutron porosity (TNPH) 1190 and thermal alpha factor (TALP) 1188, according to an example embodiment.
• TNPH thermal neutron porosity
• TBP thermal alpha factor
• the alpha factor represents the ratio between TNPH and the apparent near thermal detector 972 porosity that is used to obtain an answer with a higher vertical resolution.
• the alpha factor represents therefore the discrepancy between TNPH and the less accurate porosity that can be obtained from the near thermal detector 972 count rate.
• a drop in the alpha factor indicates that the near detector porosity differs more from the ratio porosity.
• the alpha factor can have low values in open hole. This can be overcome by deriving a more accurate single detector porosity algorithm and/or by basing the alpha factor on a more complex function of the ratio porosity and the near thermal neutron porosity.
• Figure 12 is a graph plotting depth versus an exemplary Near/Far thermal count rate ratio 1294 and also an exemplary (Near Thermal )/(Near epithermal) count rate ratio 1292, according to an example embodiment. As shown, the ratio of the two near count rates in this example shows a clear indication as the tool enters casing. Accordingly, in some embodiments, the (Near Thermal)/(Near epithermal) count rate ratio can probably be exploited as an indicator.
• a deltaphi i.e. the difference between the near and near/far thermal porosities
• a casing indicator which could be analogous to the use of deltaRho in the case of density.
• Another example can be to use the relative change (e.g., difference, ratio or other functional form) of the apparent porosities derived from all three detector count rates as an indicator.
• epithermal slowing down time SDT
• Sigma can be used as further indicators, as the near epithermal/thermal ratio can serve as an indication of Sigma.
• the above solutions can be used with neural networks. Additionally, using local knowledge, tighter limits can be imposed on the measurements.
• other types of measurements in the tool string can be used to determine whether the tool is deployed, such as induction, phasor-induction, acoustic, nuclear magnetic resonance and/or sonic measurements. In some embodiments, if the measurement made is below the density tool 212, then the fact that the tool below has been deployed may not be a certain indication that the tool above has been deployed.
• an algorithm can be used to indicate to the tool whether it should be powered up, open the caliper arm 232 and start acquisition. If the tool can detect by itself, whether it is outside of the drill pipe, the deployment can be made more efficient and the risk of damage to the tool or premature depletion of the battery will decrease.
• the new algorithm can complement or supersede the approaches already in place.
• Figure 13 is a flow diagram of an auto-detect algorithm or method according to an example embodiment.
• the time can be set when initializing the tool before lowering it into drill pipe.
• the timer could start once a certain pressure (or possibly temperature) is reached. This may require a pressure (temperature) sensor and minimal electronics to be continuously enabled.
• step 1305 a minimum amount of time has elapsed.
• step 1310 the tool string (or at least a predetermined tool in the string) will wake up and power up.
• step 1315 the tool waits for all the loops to stabilize so that reliable measurements can be made.
• steps can be performed to ensure there has not been a hardware failure to prevent additional damage and/or wasted time waiting for all loops to stabilize.
• step 1320 the density measurement (and any others) are checked to determine whether the tool (or at least the density or other appropriate section) is outside the drill pipe.
• step 1325 the method 1300 determines whether the density section (or other appropriate section) has been deployed from the drill pipe.
• step 1330 the method 1300 branches to step 1330, where it waits for a predetermined time (enough to allow full deployment to make sure that any downward movement due to the deployment has stopped). If the measurements indicate that the tool has not yet been deployed set a time for the next test and power down, the method branches to step 1335, where the measurement acquisition and power are stopped, then proceeds to step 1340 where time passes until returning to step 1305.
• the method 1300 determines in step 1345 whether caliper was successfully opened. In other words, in an example embodiment, the method 1300 determines whether the caliper reading indicates that the tool is outside the drill pipe, as discussed above.
• step 1350 the caliper is closed, and then proceeds to step 1340. If, however, the measurement indicates that the caliper could open, the method 1300 branches to step 1355, where the caliper proceeds to make the measurement.
• some or all of the foregoing techniques can be used to create a test to determine whether the tool has been deployed.
• the detailed parameters for the various tests can only be defined after some modeling and experimentation. Table 1, shown below, lists an example set of required experiments and modeling, with conditions for density detector vote according to an exemplary embodiment.
• the density check needs to assure in multiple ways that the tool is deployed. Additionally, precautions may need to be taken to allow acquisition if a sensor has failed.
• the proposed approach is based on the following conditions to allow opening the caliper: (1) there need to be at least two "yes" votes for opening the caliper; and (2) there is no veto. Additionally, in some embodiments, if the long-spaced hardware shows a failure, the caliper may not be opened but acquisition can be enabled to make sure that the measurements continue. In some example embodiments, once the caliper has opened no further checks are performed. Additionally, if the short-spaced hardware fails, a single vote can be needed to open the caliper, since a usable answer can often be obtained with the long-spaced density alone.
• the decision can be made based on neutron measurements (see above) or other measurements in the tool (sonic, resistivity) which are all sensitive to the presence of the drill pipe surrounding the tool, including resistivity measurements, sonic measurements, NMR measurements, dedicated sensor or magnet for pipe detection, a sensor on or near density pad, a sensor in other parts of the stool string, and a sensor configured to detect latching of the tool
• the invention can comprise a computer program that embodies the functions described herein and illustrated in the flow charts.
• a computer program that embodies the functions described herein and illustrated in the flow charts.
• the invention should not be construed as limited to any one set of program instructions.
• a skilled programmer would be able to write such a program to implement an embodiment of the disclosed invention based on the flow charts and associated description in the application text. Therefore, disclosure of a particular set of program code instructions is not considered necessary for an adequate understanding of how to make and use the invention.
• the invention can be used with computer hardware and software that performs the methods and processing functions described above. Specifically, in describing the functions, methods, and/or steps that can be performed in accordance with the invention, any or all of these steps can be performed by using an automated or computerized process.
• the systems, methods, and procedures described herein can be embodied in a programmable computer, computer executable software, or digital circuitry.
• the software can be stored on computer readable media.
• computer readable media can include a floppy disk, RAM, ROM, hard disk, removable media, flash memory, memory stick, optical media, magneto-optical media, CD-ROM, etc.
• Digital circuitry can include integrated circuits, gate arrays, building block logic, field programmable gate arrays (FPGA), etc.

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• 2011
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